This application is based upon and claims the benefit of priority from the prior Japanese Patent Applications No. 2000-227320, filed Jul. 27, 2000; and No. 2001-157484, filed May 25, 2001, the entire contents of both of which are incorporated herein by reference.
1. Field of the Invention
The present invention relates to a magnetic memory.
2. Description of the Related Art
A magnetoresistance effect device using a magnetic film has already been used as a magnetic head or a magnetic sensor. Moreover, it is also proposed to use the magnetoresistance effect device as a magnetic memory (magnetoresistance effect memory), and the like. In the magnetic memory, a magnetic memory using a ferromagnetic tunnel junction is expected to realize a nonvolatile storage, and a writing or reading access time less than 10 nsec, reading and writing endurance exceeding 1015 times, and small cell size like DRAM.
To realize such a magnetic memory using the ferromagnetic tunnel junction, a sufficient magnetoresistance ratio is necessary. In recent years, the magnetoresistance ratio of 20% or more has been achieved in the ferromagnetic tunnel junction. Therefore, expectation of realizing such a magnetic memory is increased more and more.
For example, a ferromagnetic tunnel junction obtained by forming a thin Al film having a thickness of 0.7 nm to 2.0 nm on a ferromagnetic layer, exposing the surface of the film to an oxygen glow electric discharge or an oxygen gas to form a tunnel barrier layer of Al2O3, and further forming a ferromagnetic layer has been proposed. According to the ferromagnetic tunnel junction, the magnetoresistance ratio of 20% or more is obtained (J. Appl. Phys. 79, 4724 (1996)). Moreover, a structure of a ferromagnetic single tunnel junction has also been proposed in which one layer of a pair of ferromagnetic layers is combined with an antiferromagnetic layer to form a magnetization pinned layer (Jpn. Pat. Appln. KOKAI Publication No. 10-1998).
As described above, in the ferromagnetic single tunnel junction, the magnetoresistance ratio of 20% or more can be obtained. However, as compared with competing memories such as FeRAM and flash memory, the magnetic memory using the ferromagnetic single tunnel junction has a problem that power consumption on writing is large.
To solve the problem, a solid magnetic memory has been proposed in which a thin film of a high permeability material is formed around a writing wiring (U.S. Pat. Nos. 5,659,499, 5,956,267, and 5,940,319, and International Patent Application No. WO00/10172). According to this magnetic memory, since the high permeability film is formed around the wiring, a current value necessary for writing information to a magnetic recording layer can efficiently be reduced. Moreover, according to the magnetic memory, since a magnetic flux generated by the current does not extend to the outside of the high permeable magnetic film, even a cross talk can be inhibited.
However, in the magnetic memory disclosed in the U.S. Pat. No. 5,659,499, a magnetic field cannot uniformly be applied to the whole recording layer of a magnetoresistance effect film. Moreover, in the magnetic memory disclosed in the U.S. Pat. Nos. 5,956,267 and 5,940,319, when a structure of the magnetic recording layer positioned between a pair of magnetization pinned layers like in a dual spin valve type double tunnel junction as described later is used, it is difficult to efficiently apply the magnetic field to the magnetic recording layer. Furthermore, the magnetic memory disclosed in the International Patent Application No. WO00/10172 has an ideal structure for applying the magnetic field to the magnetic recording layer, but it is remarkably difficult to manufacture the structure.
Moreover, in addition to the aforementioned ferromagnetic single tunnel junction, a ferromagnetic tunnel junction in which a magnetic particle is dispersed in a dielectric material, and a ferromagnetic double tunnel junction (continuous film) have also been proposed. Even in these ferromagnetic tunnel junctions, the magnetoresistance ratio of 20% or more is obtained (Phys. Rev. B 56(10), R5747 (1997)., Applied Magnetics Journal 23, 4-2 (1999), Appl. Phys. Lett. 73(19), 2829(1998)). Additionally, according to the ferromagnetic double tunnel junction, the magnetoresistance ratio generated by increasing a voltage value applied to the magnetic tunnel junctions can be prevented from decreasing in order to obtain a desired signal voltage value.
However, the ferromagnetic double tunnel junction also has a problem that the power consumption on writing is large similarly as the ferromagnetic single tunnel junction. Moreover, when the ferromagnetic double tunnel junction is used, the magnetic recording layer is held between a pair of tunnel barrier layers and a pair of magnetization pinned layers. Therefore, even when the method disclosed in the aforementioned U.S. patent is applied, an electric current magnetic field cannot efficiently act on the magnetic recording layer. That is, the magnetic memory using the ferromagnetic double tunnel junction has a problem that the power consumption on writing is remarkably large.
An object of the present invention is to provide a magnetic memory in which a power consumption on writing can be reduced.
According to a first aspect of the present invention, there is provided a magnetic memory comprising first and second wirings intersecting each other and positioned apart from each other, a magnetoresistance effect film positioned between the first and second wirings and comprising a magnetic recording layer configured to reverse a magnetization direction thereof by changing a direction of a magnetic field, which is generated by passing writing currents through the first and second wirings, between a first direction and a second direction different from the first direction, a magnetization pinned layer configured to hold the magnetization direction thereof when the direction of the magnetic field is changed between the first direction and the second direction, and a nonmagnetic layer intervening between the magnetic recording layer and the magnetization pinned layer, and a first magnetic film comprising a first portion facing the magnetoresistance effect film with the first wiring interposed therebetween and a pair of second portions positioned on both sides of the first wiring and magnetically connected to the first portion, each of the first and second portions comprising either one of a high saturation magnetization soft magnetic material containing cobalt and a metal-nonmetal nano-granular film.
According to a second aspect of the present invention, there is provided a magnetic memory comprising first and second wirings intersecting each other and positioned apart from each other, a magnetoresistance effect film positioned between the first and second wirings and comprising a magnetic recording layer configured to reverse a magnetization direction thereof by changing a direction of a magnetic field, which is generated by passing writing currents through the first and second wirings, between a first direction and a second direction different from the first direction, first and second magnetization pinned layers sandwiching the magnetic recording layer and each configured to hold a magnetization direction thereof when the direction of the magnetic field is changed between the first direction and the second direction, a first nonmagnetic layer intervening between the first magnetization pinned layer and the magnetic recording layer, and a second nonmagnetic layer intervening between the second magnetization pinned layer and the magnetic recording layer, and a first magnetic film comprising a first portion facing the magnetoresistance effect film with the first wiring interposed therebetween and a pair of second portions positioned on both sides of the first wiring and magnetically connected to the first portion, each of the first and second portions comprising either one of a high saturation magnetization soft magnetic material containing cobalt and a metal-nonmetal nano-granular film.
According to a third aspect of the present invention, there is provided a magnetic memory comprising first and second wirings intersecting each other and positioned apart from each other, a magnetoresistance effect film positioned between the first and second wirings and comprising a magnetic recording layer configured to reverse a magnetization direction thereof by changing a direction of a magnetic field, which is generated by passing writing currents through the first and second wirings, between a first direction and a second direction different from the first direction, first and second magnetization pinned layers sandwiching the magnetic recording layer and each configured to hold a magnetization direction thereof when the direction of the magnetic field is changed between the first direction and the second direction, a first nonmagnetic layer intervening between the first magnetization pinned layer and the magnetic recording layer, and a second nonmagnetic layer intervening between the second magnetization pinned layer and the magnetic recording layer, and a first magnetic film comprising a first portion facing the magnetoresistance effect film with the first wiring interposed therebetween and a pair of second portions positioned on both sides of the first wiring and magnetically connected to the first portion, the second portions being in contact with one of the first and second nonmagnetic layers which is closer to the first magnetic film than the other of the first and second nonmagnetic layers.
According to a fourth aspect of the present invention, there is provided a magnetic memory comprising first and second wirings intersecting each other and positioned apart from each other, a magnetoresistance effect film positioned between the first and second wirings and comprising a magnetic recording layer configured to reverse a magnetization direction thereof by changing a direction of a magnetic field, which is generated by passing writing currents through the first and second wirings, between a first direction and a second direction different from the first direction, first and second magnetization pinned layers sandwiching the magnetic recording layer and each configured to hold a magnetization direction thereof when the direction of the magnetic field is changed between the first direction and the second direction, a first nonmagnetic layer intervening between the first magnetization pinned layer and the magnetic recording layer, and a second nonmagnetic layer intervening between the second magnetization pinned layer and the magnetic recording layer, and a first magnetic film comprising a first portion facing the magnetoresistance effect film with the first wiring interposed therebetween and a pair of second portions positioned on both sides of the first wiring and magnetically connected to the first portion, the magnetic recording layer being positioned between the second portions.
In the first to fourth aspects of the present invention, when the current is passed through the first wiring, the first magnetic film provides a flux path for a generated magnetic force line or magnetic flux. Also, the magnetic memory according to first to fourth aspects of the present invention may have a ferromagnetic tunnel junction in which the nonmagnetic layer is a nonmagnetic tunnel layer (tunnel barrier layer), or else, may have a so-called giant magnetoresistance (GMR) effect film in which the nonmagnetic layer is not the tunnel barrier layer.
When the first to fourth aspects of the present invention define a ferromagnetic tunnel junction having a structure in which the magnetization pinned layer with the fixed magnetization direction, nonmagnetic tunnel layer, and magnetic recording layer with the reversible magnetization direction are successively laminated, this ferromagnetic tunnel junction includes not only a ferromagnetic single tunnel junction but also a ferromagnetic multiple tunnel junction. Alternatively, when the first to fourth aspects of the present invention define a ferromagnetic tunnel junction having a structure in which the first magnetization pinned layer with the fixed magnetization direction, first nonmagnetic tunnel layer, magnetic recording layer with the reversible magnetization direction, second magnetization pinned layer with the fixed magnetization direction, and second nonmagnetic tunnel layer are successively laminated, this ferromagnetic tunnel junction includes a ferromagnetic multiple tunnel junction.
When the magnetoresistance effect film has the first and second nonmagnetic layers, the first magnetic film can be magnetically connected to the magnetic recording layer via either nonmagnetic layer. This can be realized, for example, by employing the following structure. That is, a width of the first nonmagnetic layer and magnetic recording layer are set to be larger and the width of the first magnetization pinned layer is set to be smaller with respect to a distance between the surfaces of the first and second portions facing to each other. Thereby, the main surface of the first nonmagnetic layer is partially exposed in correspondence with the first and second portions. In this case, when the exposed portions of the first nonmagnetic layer are brought in contact with the first and second portions, the magnetic film is magnetically connected to the magnetic recording layer via the first nonmagnetic layer. Therefore, the magnetic flux generated by passing the current through the first wiring and passed through the first magnetic film can efficiently be applied to the magnetic recording layer. As a result, information can be written even when an amount of a current passed through the first wiring is small, and power consumption required for writing the information can be reduced.
Moreover, when the magnetoresistance effect film has the first and second nonmagnetic layers, the magnetic film providing the flux path can also be magnetically connected to the magnetic recording layer by the following structure. That is, the width of the first magnetization pinned layer, first nonmagnetic layer and magnetic recording layer is reduced, and set to be not more than the distance between the surfaces of the first and second portions facing to each other. In this case, when the magnetic recording layer is positioned between the first and second portions, the magnetic film can be magnetically connected to the magnetic recording layer. Therefore, the information can be written even when the amount of the current passed through the first wiring is small, and the power consumption required for writing the information can be reduced.
In the first to fourth aspects of the present invention, a length of the first magnetic film along a longitudinal direction of the first wiring may be 1.2 times or more, or 1.5 times or more the length of the magnetoresistance effect film along the longitudinal direction of the first wiring. Similarly, the length of the second magnetic film along the longitudinal direction of the second wiring may be 1.2 times or more, or 1.5 times or more the length of the magnetoresistance effect film along the longitudinal direction of the second wiring. In this case, the magnetic field can more effectively be applied to the magnetic recording layer.
The first and second wirings may contain one material selected from the group consisting of aluminum, copper, tungsten, and an alloy of these metals. Alternatively, the first and second wirings may have a multilayered structure including the nonmagnetic layer and high saturation magnetization soft magnetic material layer, such as a laminated structure of a Cu layer and CoFeNi layer. When the wirings are made of the material mainly containing Cu and the first and second magnetic films are alloy based films containing Co or Coxe2x80x94Fe as a main component, Cu and Co or Coxe2x80x94Fe are hardly dissolved in each other. Therefore, even when a usual heat treatment process is performed or an excessively large current is passed, Cu contained in the wiring and Co or Coxe2x80x94Fe contained in the magnetic film are not mutually diffused. Therefore, it is unnecessary to dispose a barrier metal between the wiring and the magnetic film.
Each of the first and second magnetic films can comprise a Coxe2x80x94Fe alloy film, a Coxe2x80x94Fexe2x80x94Ni alloy film, an amorphous material film such as a Coxe2x80x94(Zr, Hf, Nb, Ta, Ti) film, a (Co, Fe, Ni)xe2x80x94(Si, B) based film, a (Co, Fe, Ni)xe2x80x94(P, Al, Mo, Nb, Mn) based film and a (Co, Fe, Ni)xe2x80x94(Si, B)xe2x80x94(P, Al, Mo, Nb, Mn) based film, and metal-nonmetal nano-granular films such as a (Fe, Co)xe2x80x94(B, Si, Hf, Zr, Sm, Ta, Al)xe2x80x94(F, O, N) based film. In more detail, these magnetic films may also comprise the high saturation magnetization soft magnetic material film containing a Co element, or the metal-nonmetal nano-granular films such as a (Fe, Co)xe2x80x94(B, Si, Hf, Zr, Sm, Ta, Al)xe2x80x94(F, O, N) based film.
It is noted that the metal-nonmetal nano-granular film may have a structure in which metal granules are dispersed in a nonmetal matrix. Alternatively, the metal-nonmetal nano-granular film may have a structure in which nonmetal granules are dispersed in a metal matrix.
The magnetization pinned layer and magnetic recording layer may contain Fe, Co, Ni, an alloy of these metals, and half metals such as NiMnSb, PtMnSb and Co2MnGe. A saturation magnetization Bs of the magnetic recording layer may be more than 5 kG.
Moreover, examples of the material of the nonmagnetic tunnel layer include Al2O3, AlN, MgO, SiO2, GaO, LaAlO3, MgF2, and CaF2.
In the first to fourth aspects of the present invention, a magnetic film similar to the magnetic film around the first wiring may also be provided around the second wiring. Moreover, the magnetic film in the position of the ferromagnetic tunnel junction may also be extended over the whole wiring.
In the first to fourth aspects of the present invention, with respect to a size in a cross-section vertical to the longitudinal direction of the wiring around which the magnetic film is provided, assuming that the length of the magnetic film in an opening width direction is 11, and the length thereof in a vertical direction is 12, an aspect ratio 12/11 may be larger than 1. In this case, the current magnetic field is strengthened. This aspect ratio 12/11 may be larger than 1.5 and smaller than 5, or else, larger than 2 and smaller than 5.
The magnetic memory of the first to fourth aspects of the present invention can further comprise a sense current control device configured to control a sense current passed through the magnetic memory in order to read the information stored in the magnetic memory. As the sense current control device, a transistor or a diode can be used.